Method for the selective hydrogenation of a pyrolysis gasoline feedstock with a three-phase reactor

Abstract

This invention has as its object a method for selective hydrogenation of a feedstock comprising a pyrolysis gasoline carried out in a three-phase reactor.

The invention claimed is: 
     
       1. Method for selective hydrogenation of at least polyunsaturated compounds in a liquid phase feedstock comprising a pyrolysis gasoline, which comprises polyunsaturated compounds, in the presence of a gaseous phase comprising hydrogen, wherein the hydrogenation is performed in a three-phase reactor having a reaction zone volume in the presence of a selective hydrogenation catalyst that is dispersed in the liquid phase, the hydrogenation being performed at a molar ratio of (hydrogen)/(polyunsaturated compounds to be hydrogenated) of between 0.5 and 10, at a temperature of between 0° C. and 200° C., at an hourly volumetric flow rate (V.V.H.)—that is defined as a ratio of volumetric flow rate of the feedstock at 15° C. to total volume of the reaction zone—of between 0.5 h −1  and 100 h −1 , and at a pressure of between 1 MPa and 6.5 MPa;
 said method comprising:
 a) continuously introducing said liquid phase feedstock and the gaseous phase comprising hydrogen into a three-phase reactor containing a selective hydrogenation catalyst that is dispersed into the liquid phase, 
 b) drawing a gaseous phase comprising hydrogen off at the top of the reactor, 
 c) drawing a suspension from the reactor and introducing it into a separation zone in such a way as to separate either a phase containing the pyrolysis gasoline that is at least partially selectively hydrogenated and a catalyst-concentrated phase, or a C8− phase that is at least partially selectively hydrogenated and a catalyst-concentrated phase. 
 
 
     
     
       2. Method according to  claim 1 , in which the selective hydrogenation catalyst is between 1 and 1,000 μm in size. 
     
     
       3. Method according to  claim 1 , in which the liquid phase has a surface liquid velocity (slv) of between 1 mm/s and 10 m/s. 
     
     
       4. Method according to  claim 1 , in which the selective hydrogenation catalyst in the three-phase reactor has a concentration in relation to the feedstock of between 5% and 40% by weight. 
     
     
       5. Method according to  claim 1 , wherein the hydrogenation is carried out at a molar ratio of (hydrogen)/(polyunsaturated compounds to be hydrogenated) of between 1 and 2, at a temperature of between 80° C. and 180° C., at an hourly volumetric flow rate (V.V.H.) of between 1 h −1  and 6 h −1 , and at a pressure of between 2 MPa and 6 MPa. 
     
     
       6. Method according to  claim 1 , in which the selective hydrogenation catalyst comprises a metal from group VIII on a porous substrate formed by at least one oxide. 
     
     
       7. Method according to  claim 1 , wherein, in the separation zone, a phase containing the pyrolysis gasoline that is at least partially selectively hydrogenated and a catalyst-concentrated phase are separated. 
     
     
       8. Method according to  claim 7 , in which the separation in the separation zone comprises a decanting. 
     
     
       9. Method according to  claim 1 , wherein, in the separation zone, a C8-phase that is at least partially selectively hydrogenated and a catalyst-concentrated phase are separated. 
     
     
       10. Method according to  claim 9 , in which the separation in the separation zone comprises an evaporation. 
     
     
       11. Method according to  claim 7 , in which at least a part of the catalyst-concentrated phase is recycled to the three-phase reactor. 
     
     
       12. Method according to  claim 1 , in which the pyrolysis gasoline that is at least partially selectively hydrogenated or the C8− phase that is at least partially selectively hydrogenated is/are subjected to a hydrodesulfurization that is carried out in a gaseous phase in a fixed-bed reactor in the presence of a gaseous phase comprising hydrogen and a hydrodesulfurization catalyst. 
     
     
       13. Method according to  claim 1 , wherein the feedstock comprising a pyrolysis gasoline comprises: 5 to 15% by weight of paraffins, 50 to 65% by weight of aromatic compounds, 5 to 15% by weight of monoolefins, 15 to 25% by weight of diolefins and 2 to 8% by weight of alkenylaromatic compounds. 
     
     
       14. Method according to  claim 1 , wherein the feedstock comprising a pyrolysis gasoline comprises a C5-C12 fraction.